REVISED DESCRIPTION OF PENICILLIUM ULAIENSE AND ITS ROLE AS A PATHOGEN OF CITRUS-FRUITS

Penicillium ulaiense causes whisker mold, a recently described post-ha rvest disease of citrus fruits. A new, more comprehensive description of the fungus and related taxonomic information are given. This descri ption is based on examinations of the type isolate and 33 other isolat es from citrus fruits in seven citrus-growing areas of the world. P. u laiense was confirmed unique from P. italicum, the cause of citrus blu e mold, by arbitrarily primed polymerase chain reaction analysis and m orphological criteria. P. ulaiense, P. italicum, and P. digitatum (the cause of citrus green mold) showed similar temperature-growth relatio nships, but P. ulaiense grew more slowly. P. ulaiense was pathogenic b ut only moderately virulent to commercial varieties of citrus. P. ital icum and P. digitatum formed lesions 80 mm in diameter on lemons and o ranges three to five times faster than did P. ulaiense. The number of conidia required to produce decay in 50% of inoculated lemons was 100- 1,000 times greater for P. ulaiense than those required for P. italicu m and P. digitatum. Isolates of P. ulaiense collected in the United St ates were relatively resistant to the fungicides imazalil, thiabendazo le, and o-phenylphenol; mean fungicide concentrations producing 50% in hibition for 17 isolates were 0.7 (+/-0.2), 45.7 (+/-4.1), and 12.5 (/-5.4) mu g/ml, respectively. Growth of all isolates collected in othe r countries was inhibited completely by 0.2 mu g of imazalil or 10 mu g of thiabendazole per milliliter. P. ulaiense was isolated frequently from California packinghouses but not from citrus groves.